Heating appliance

Description

[0001] The present invention relates to a heating appliance such as a microwave oven or an electric oven for heating objects including food.

[0002] Conventionally, a microwave oven with a moisture sensor determines when the food is completely heated by detecting the amount of vapour generated by the heated food. The output from the moisture sensor increases as vapour is generated from the heated food. When the output reaches a specified value (detection point), additional heating time required for completing the food is calculated on the basis of a constant stored in an LSI. The oven then continues heating the food for the calculated period of time and then stops heating so that optimally heated food can be obtained. The constant is different for different foods. For a certain kind of food, the user may be required to open the oven door in the middle of the heating process and to reverse and/or change the position of the food for more uniform heating. Usually, this intermediate food handling operation is carried out when the sensor output reaches the detection point level. For some foods, however, the intermediate food handling operation may be necessary at a particular time. Frozen hamburger patties which are among the list of foods to be cooked by a sensor-equipped oven is an example. They need to be reversed and/or moved in the middle of cooking so as to be uniformly heated. The sensor output increase for this food is, however, very slow. Therefore, if this food is heated until the output reaches the detection point, it may be overheated locally, depending upon the quantity. If the food is reversed and/or moved at this stage, it cannot be expected to be optimally heated. That is, depending upon the quantity, the food may be required to be reversed and/or moved earlier than the detection point. One to three frozen hamburger patties can be optimally cooked if they are reversed and/or moved at the detection point. Four to six hamburger patties could be overheated locally if they were not moved until the detection point; they must be moved earlier than the detection point.

[0003] Fig. 2 shows the relationship between sensor output and heating time for four or more hamburger patties. Each is supposed to be heated in a case.

[0004] Here, the detection point level of sensor output is considered to be 10 bits. The oven is designed to carry out additional heating after the sensor output reaches 10 bits. When the oven door is opened to take out the hamburger patties and reverse and/or change the positions in the middle of heating, part of the vapour generated from the food and accumulated within the heating chamber flows out of the oven, so that the output of the detector sensor drops. It begins rising when the food is returned and heated again in the oven. Therefore, if this intermediate food handling operation is conducted before the sensor output reaches the detection point, the time required for the output to reach the detection point is a little longer than that for the case where the oven door is not opened until the detection point is reached. The arithmetic operation for calculating the additional heating time required after the detection point is reached takes account of this time lag.

[0005] If this intermediate food handling operation is carried out before the detection point is reached, not outside the oven but in the oven, vapour and heat accumulated within the case are released all at once into the heating chamber when the case covers are opened. The vapour thus released partly flows into the exhaust duct leading to the detector sensor which is installed immediately above the heating chamber. Moreover, the magnetron cooling fan which generates an air stream in the heating chamber stops, when the door is opened, causing the vapour to stay in a part of the exhaust duct.

[0006] If the door is closed and the heater is actuated, the magnetron is energized and the magnetron cooling fan starts operating. This generates an air current which causes the vapour remaining in the exhaust duct to be led to the detector sensor. When the sensor output at the intermediate food handling operation time (TA) is just below the detection point as shown in Fig. 2, the sensor output will reach the detection point immediately after the heating is resumed. As a result, the oven will be turned off before the food is sufficiently heated.

[0007] In view of the above problem with conventional cooking appliances, it would be desirable to provide a cooking appliance capable of heating food optimally even if the oven door is opened to reverse and/or change the position of the food in the heating chamber at a specified time in the middle of the heating process before the sensor output reached the detection point.

[0008] According to the present invention there is provided a heating appliance having a sensor for detecting an environmental condition which varies in accordance with the heating state of one or more articles being heated by the appliance, and a heating control means for controlling the heating of the article or articles in accordance with the sensor output, said heating control means being adapted to respond to the sensor output reaching a predetermined level, characterised in that said heating control means is adapted so that if heating is interrupted before said output reaches said predetermined level and subsequently resumed, the heating control means is caused to be non-responsive to the sensor output for a predetermined period following the resumption of heating.

[0009] Accordingly, the user can reverse and/or change the position of the articles at a timing most suitable to obtain uniformly heated articles, irrespective of the quantity. The predetermined period for which the sensor output is inhibited may be, for example, about 30 to 60 seconds.

[0010] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein:

Fig. 1 is a schematical drawing of the microwave oven according to an embodiment of the present invention viewed from the front;

Fig. 2 is a graph showing the relationship between the output of the detector element and the heating time for four hamburgers; and

Fig. 3 is a flowchart of the procedure for controlling the microwave oven of Fig. 1 in heating food.

[0011] Fig. 1 is a schematical drawing showing a microwave oven 1 of an embodiment of the present invention viewed from the front. The housing 2 of the microwave oven 1 contains a cooking chamber 4 in which food 3 can be heated. The food 3 is placed on a turntable 5. The housing 2 has a door 6 for airtight closing of the cooking chamber 4. Electromagnetic radiation from heater means 7 such as a magnetron is supplied through a wave guide 8 to the cooking chamber 4, to heat the food 3. An exhaust duct (not shown) is provided in the upper part of the housing 2 so that vapour generated from the food 3 heated in the cooking chamber 4 is led to the oven exterior. A detector element 9 is provided in the exhaust duct to detect the amount of vapour. The signal output from the detector element 9 is sent to a control circuit 10 which is connected with a setter 20 retaining constants for various foods. When the signal output from the detector element 9 reaches a predetermined first discrimination level 41 (See Fig. 2), the control circuit 10 reads the constant of the food being heated, stored in the setter 20. Using this constant, the control circuit 10 calculates the appropriate additional heating time for the food and controls the heater means 7 to heat the food additionally for the calculated period of time. The control circuit 10 is connected to an alarm buzzer 11 which informs the user of the intermediate food handling time, that is the time for opening the oven door 6 to reverse and/or change the position of the food 3.

[0012] Fig. 2 shows the relationship between the output of the detector element 9 and the heating time for four frozen hamburger patties (hereinafter called hamburgers). Fig. 3 is a flowchart of the procedure for cooking food in a microwave oven 1.

[0013] The operation starts in step n1, and the heater 7 heats the food 3 in step n2. In step n3, it is judged whether or not the predetermined time W1 has elapsed. The time W1 is usually shorter than the time required for the output of the detector element 9 to reach the detection point level 21. For four or more hamburgers, for example, the time W1 is about three minutes. when the time W1 has elapsed, the operation process moves to step n4 where the buzzer 11 sounds an alarm, informing the user of the intermediate food handling time. Then the user opens the door 6, reverses and/or changes the position of the food and closes the door 6. At the same time as the heating operation is resumed, the operation process moves to step n5 where it is judged whether or not the predetermined period W2 has elapsed since heating was resumed after the intermediate food handling operation. For the four or more hamburgers, the time W2 is about 30 seconds.

[0014] In step n7, it is judged whether or not the signal output from the detector element 9 has reached the detection point level il. In this embodiment of the invention, the output of 10 bits is selected for the detection point level B1. If the detection point level 41 has not been reached in step n7, the heater means 7 continues heating the food 3 until the detector output reaches the level .21. when the level 41 is reached, the control circuit 10 reads the constant for the food from the setter 20 and calculates the appropriate additional heating time "t". In step n8, the food 3 is further heated by the heater means 7 for the time "t". Then the heater means 7 is stopped in step n9 and the heating process ends in step n10.

[0015] As understood from the above description, data are not read for the specified period of time after the intermediate food handling operation. Therefore, if the detector output reaches 10 bits or the detection point level within 30 seconds after the intermediate food handling operation which was conducted before the output reaches the detection point level, or specifically after the four hamburgers have been heated for three minutes, the control circuit ignores the signal output, thus preventing the heater means from being turned off before the food is heated sufficiently.

[0016] The above embodiment concerns the case where frozen hamburger patties are heated in the cooking heater. The present invention, however, may be used for heating any other object if it can be heated.

[0017] When heating is resumed after the intermediate food handling operation conducted before the detector output reaches a specified value fixed for each food (in other words, after the food is heated for a predetermined period of time), the control circuit does not read detector signal output for a specified period of time.

[0018] Since the control circuit does not read the detector signal output for the specified period of time after the heating operation is resumed following the intermediate food handling operation, vapour accumulated in the exhaust duct leading to the detector element is allowed to be released outside the oven, resulting in the amount of vapour in the exhaust duct being stabilized. This enables the detector element to sense accurately the amount of vapour generated in the heating chamber and facilitates the user to carry out the intermediate food handling operation at the optimal timing for the food, irrespective of the detection point level, whereby the food can be heated uniformly and optimally.

[0019] Even if the oven door is opened before the detector output reaches the detection point level, the detector element senses accurately the amount of vapour so that additional heating can be carried out for the period most suitable to yield optimally cooked food, and that food of any quantity can be heated uniformly because intermediate food handling operation timing can be selected appropriately according to the quantity of the food.

Claims

1. A heating appliance having a sensor (9) for detecting an environmental condition which varies in accordance with the heating state of one or more ar- tides being heated by the appliance, and a heating control means (10) for controlling the heating of the article or articles in accordance with the sensor output, said heating control means being adapted to respond to the sensor output reaching a predetermined level, characterised in that said heating control means is adapted so that if heating is interrupted before said output reaches said predetermined level and subsequently resumed, the heating control means is caused to be non-responsive to the sensor output for a predetermined period following the resumption of heating.

2. A heating appliance according to claim 1 wherein said heating control means (10) is adapted to respond to the sensor output reaching the predetermined level to determine the length of an additional heating period.

3. A heating appliance according to claim 1 or claim 2 wherein said sensor is a vapour sensor located in the region of a gas exhaust from a heating chamber (4) of the appliance.

Ansprüche

1. Heizapparat mit einem Sensor (9) zur Erfassung einer Umgebungsbedingung, die sich entsprechend dem Erwärmungszustand eines oder mehrerer durch den Heizapparat beheizter Artikel ändert, und einer Heizungs-Steuereinrichtung (10) zur Steuerung der Beheizung des Artikels oder der Artikel entsprechend dem Ausgangssignal des Sensors, wobei die Steuereinrichtung darauf anspricht, daß das Ausgangssignal des Sensors einen vorgegebenen Pegel erreicht, dadurch gekennzeichnet, daß die Heizungs-Steuereinrichtung so ausgelegt ist, daß in dem Fall, daß der Heizvorgang unterbrochen wird, bevor das Ausgangssignal den vorgegebenen Pegel erreicht, und anschließend wieder fortgesetzt wird, die Steuereinrichtung während eines bestimmten Zeitintervalls nach der Wiederaufnahme des Heizvorgangs nicht auf das Ausgangssignal des Sensors anspricht.

2. Heizapparat nach Anspruch 1, dadurch gekennzeichnet, daß die Heizungs-Steuereinrichtung (10) auf das Erreichen des vorgegebenen Pegels durch das Sensor-Ausgangssignal anspricht, um die Länge einer zusätzlichen Heizperiode zu bestimmen.

3. Heizapparat nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Sensor ein Dampfsensor ist, der im Bereich eines Gasauslasses einer Heizkammer (4) des Heizapparates angeordnet ist.

Revendications

1. Appareil de chauffage comportant un capteur (9) servant à détecter une condition de l'environnement, qui varie en fonction de l'état de chauffage d'un ou de plusieurs articles chauffés par cet appareil, et des moyens (10) de commande du chauffage servant à commander le chauffage du ou des articles conformément au signal de sortie du capteur, lesdits moyens de commande du chauffage étant adaptés pour répondre au fait que le signal de sortie du capteur atteint un niveau prédéterminé, caractérisé en ce que lesdits moyens de commande du chauffage sont adaptés de telle sorte que, si le chauffage est interrompu avant que ledit signal de sortie n'atteigne ledit niveau prédéterminé et qu'il est remis en marche ultérieurement, les moyens de commande du chauffage sont rendus insensibles au signal de sortie du capteur pendant un intervalle de temps prédéterminé à la suite de la remise en marche du chauffage.

2. Appareil de chauffage selon la revendication 1, dans lequel lesdits moyens (10) de commande du chauffage sont adaptés pour répondre au fait que le signal de sortie du capteur atteint le niveau prédéterminé, de manière à déterminer la durée d'une période additionnelle de chauffage.

3. Appareil de chauffage selon la revendication 1 ou 2, dans lequel ledit capteur est un capteur de vapeur situé au voisinage de la sortie des gaz d'une chambre de cuisson (4) de l'appareil.

Drawing